lean4-htt/tests/lean/repr_issue.lean
2025-09-22 12:47:11 +00:00

17 lines
637 B
Text

--
def foo {m} [Monad m] [MonadExcept String m] [MonadState (Array Nat) m] : m Nat :=
tryCatch
(do modify $ fun (a : Array Nat) => a.set! 0 33;
throw "error")
(fun _ => do let a ← get; pure $ a[0]!)
def ex₁ : StateT (Array Nat) (ExceptT String Id) Nat :=
foo
def ex₂ : ExceptT String (StateT (Array Nat) Id) Nat :=
foo
-- The following examples were producing an element of Type `id (Except String Nat)`.
-- Type class resolution was failing to produce an instance for `Repr (id (Except String Nat))` because `id` is not transparent.
#eval ex₁.run' (mkArray 10 1000) |>.run
#eval ex₂.run' (mkArray 10 1000) |>.run